Mutants from cultured mouse cells, resistant to alpha-amanitin, a fungal toxin which inhibits RNA polymerase II, rifamycin AF018, and toyocamycin are being isolated. The changes in RNA metabolism in these mutants will be characterized. If any appeared to be altered in enzymes involved in transcription or RNA processing, the enzymes will be isolated and their proportion examined. BIBLIOGRAPHIC REFERENCES: Magee, B.B., J. Paoletti, and P.T. Magee. 1975. Separation of lymphocyte chromatin into template-active proteins with specificity for eukaryotic or prokaryotic RNA polymerase. Proc. Nat. Acad. Sci. (Wash). 72:4830-4834.